The granuloma which forms around the Schistosoma mansoni egg, which is a form of cellular hypersensitivity, has been shown to be the fundamental cause of the disease syndromes of chronic schistosomiasis. We have now isolated in pure form and partially characterized 3 antigens from S. mansoni eggs. Radioimmunioassays have been developed for all three. Studies of the S. mansoni egg granuloma in vitro have demonstrated secretion of 2 different lymphokines, protein synthesis which is not immunoglobulin but is largely collagen, and output of lysozomal enzymes. Using monospecific anti-eosinophil serum the kinetics of eosinophilia in schistosomiasis mansoni has been investigated and a role for the eosinophil in immunity to this parasite has been described. Finally, it has been shown that diabetes mellitus (a metabolic disease) and toxoplasmosis (an infectious disease) are intensely suppressive of the schistosome egg granuloma and other forms of cellular hypersensitivity. BIBLIOGRAPHIC REFERENCES: Warren, K.S. hepatosplenic schistosomiasis mansoni: An immunologic disease. Bull. N.Y. Acad. Med. 51: 545-550, 1975. Dumont, A.E., Becker, F.F., Warren, K.S. and Martelli, A. Regulation of spleen growth and portal pressure in hepatic schistosomiasis. Am. J. Pathol. 78: 211-220, 1975.